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From |
A Loumiotis <antonis.loumiotis@gmail.com> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: AW: mfx-Elasticity for a dummy variable |

Date |
Mon, 14 Jun 2010 12:27:47 +0300 |

Dear Nyasha, I have corrected myself previously and said it's c/T. Regards, Antonis On Thu, Jun 10, 2010 at 7:09 PM, Nyasha Tirivayi <ntirivayi@gmail.com> wrote: > Dear Antonis > > Yes you have the model correct. However, you earlier said the > elasticity was c*T instead of c/T. Which is it then? > > Kindly advise > > Regards > > Nyasha Tirivayi > Maastricht University > > On Thu, Jun 10, 2010 at 11:11 AM, A Loumiotis > <antonis.loumiotis@gmail.com> wrote: >> your model is (correct me if i'm wrong): >> >> ln(y) = a + b ln(x) + c T + dZ + error >> >> The elasticity of y with respect to T is >> (dy/y)/(dT/T)=dln(y)/(dT/T)=(dln(y)/dT)/T=c/T. >> >> So, the elasticity of y with respect to T does not depend on the means >> of ln(x) and ln(y). As I said in my previous reply it is equal to the >> coefficient of the dummy variable T divided by T (= c / T). So the >> elasticity will be equal to "c" only if you calculate it at T=1 and >> not at the mean of T. It is your call but you should consider the >> drawbacks of computing elasticities with respect to dummy(discrete) >> variables. >> >> Antonis >> >> On Wed, Jun 9, 2010 at 6:15 PM, Nyasha Tirivayi <ntirivayi@gmail.com> wrote: >>> Dear Antonis and Martin >>> >>> Thanks for your reply. If you recall my model is as follows: >>> >>> ln(y) = a + b ln(x) + T + D Z >>> >>> I intend to calculate elasticity for T at T=1 and at means of ln(x) >>> and ln(Y). And if I do that the elasticity is the same as the >>> coefficient of T. >>> >>> Should I proceed with that as the answer? >>> >>> Kindly advise >>> >>> Nyasha Tirivayi >>> Maastricht University >>> >>> On Tue, Jun 8, 2010 at 1:27 PM, A Loumiotis <antonis.loumiotis@gmail.com> wrote: >>>> Yes I agree... although one can compute it at the mean point of T >>>> which is different from 0 or 1. But as I said in my first response >>>> elasticities with respect to dummy variables have no meaningful >>>> interpretation. >>>> >>>> On Tue, Jun 8, 2010 at 2:18 PM, Martin Weiss <martin.weiss1@gmx.de> wrote: >>>>> >>>>> <> >>>>> >>>>> " ...will be the coefficient of the dummy >>>>> variable T divided by the dummy variable itself." >>>>> >>>>> >>>>> I do not get this sentence. The dummy is either 0 or 1, as you said. >>>>> Dividing by zero is not permissible, and dividing by one does not change >>>>> anything, does it? >>>>> >>>>> >>>>> >>>>> HTH >>>>> Martin >>>>> >>>>> -----Ursprüngliche Nachricht----- >>>>> Von: owner-statalist@hsphsun2.harvard.edu >>>>> [mailto:owner-statalist@hsphsun2.harvard.edu] Im Auftrag von A Loumiotis >>>>> Gesendet: Dienstag, 8. Juni 2010 13:15 >>>>> An: statalist@hsphsun2.harvard.edu >>>>> Betreff: Re: st: AW: mfx-Elasticity for a dummy variable >>>>> >>>>> The elasticity of y with respect to the dummy variable in the way that >>>>> you have defined your regression will be the coefficient of the dummy >>>>> variable T divided by the dummy variable itself. >>>>> >>>>> On Tue, Jun 8, 2010 at 2:05 PM, A Loumiotis <antonis.loumiotis@gmail.com> >>>>> wrote: >>>>>> Nyasha, >>>>>> >>>>>> The elasticity of y with respect to the dummy variable in the way that >>>>>> you have defined your regression will be the coefficient of the dummy >>>>>> variable T times the dummy variable itself. If you calculate it at >>>>>> the mean point of T then it will be different from the coefficient of >>>>>> the dummy variable. If you calculate it at T=1, it will be the same. >>>>>> >>>>>> However elasticities with respect to dummy variables have no >>>>>> meaningful interpretation because the dummy variable changes in a >>>>>> discrete fashion (from 0 to 1). >>>>>> >>>>>> Antonis Loumiotis >>>>>> >>>>>> On Mon, Jun 7, 2010 at 6:24 PM, Nyasha Tirivayi <ntirivayi@gmail.com> >>>>> wrote: >>>>>>> Dear Martin >>>>>>> >>>>>>> Thanks for the code. Now the results are different. I was using the >>>>>>> wrong code i.e mfx , dyex at(mean) instead of mfx compute, >>>>>>> varlist(logweight) dyex at(mean). >>>>>>> >>>>>>> Regards >>>>>>> >>>>>>> Nyasha Tirivayi >>>>>>> Maastricht University >>>>>>> >>>>>>> >>>>>>> >>>>>>> On Mon, Jun 7, 2010 at 9:16 AM, Martin Weiss <martin.weiss1@gmx.de> >>>>> wrote: >>>>>>>> >>>>>>>> <> >>>>>>>> >>>>>>>> What is the difference of your example to this one - where the marginal >>>>>>>> effects do seem to change: >>>>>>>> >>>>>>>> >>>>>>>> ************* >>>>>>>> sysuse auto, clear >>>>>>>> gen logprice=log(price) >>>>>>>> gen logweight=log(weight) >>>>>>>> reg logprice length logweight foreign >>>>>>>> mfx compute, varlist(logweight) dydx at(mean) >>>>>>>> mfx compute, varlist(logweight) eyex at(mean) >>>>>>>> mfx compute, varlist(logweight) dyex at(mean) >>>>>>>> mfx compute, varlist(logweight) eydx at(mean) >>>>>>>> ************* >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> HTH >>>>>>>> Martin >>>>>>>> >>>>>>>> -----Ursprüngliche Nachricht----- >>>>>>>> Von: owner-statalist@hsphsun2.harvard.edu >>>>>>>> [mailto:owner-statalist@hsphsun2.harvard.edu] Im Auftrag von Nyasha >>>>> Tirivayi >>>>>>>> Gesendet: Montag, 7. Juni 2010 02:50 >>>>>>>> An: statalist@hsphsun2.harvard.edu >>>>>>>> Betreff: st: mfx-Elasticity for a dummy variable >>>>>>>> >>>>>>>> Dear All >>>>>>>> >>>>>>>> I am trying to estimate elasticity for a dummy explanatory variable in >>>>>>>> the following model >>>>>>>> >>>>>>>> ln(y) = a + b ln(x) + T + D Z >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> I am interested in calculating the elasticity for T a dummy variable >>>>>>>> for a "treatment". What is the formula in stata? Is it mfx,dy/dx or >>>>>>>> mfx,dyex? >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> I have done mfx,dyex and the result still remains the coefficient for >>>>>>>> T. Could it be that simple? Or there is another way ? >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> Kindly advise >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> Nyasha Tirivayi >>>>>>>> >>>>>>>> Maastricht University >>>>>>>> * >>>>>>>> * For searches and help try: >>>>>>>> * http://www.stata.com/help.cgi?search >>>>>>>> * http://www.stata.com/support/statalist/faq >>>>>>>> * http://www.ats.ucla.edu/stat/stata/ >>>>>>>> >>>>>>>> >>>>>>>> * >>>>>>>> * For searches and help try: >>>>>>>> * http://www.stata.com/help.cgi?search >>>>>>>> * http://www.stata.com/support/statalist/faq >>>>>>>> * http://www.ats.ucla.edu/stat/stata/ >>>>>>>> >>>>>>> >>>>>>> * >>>>>>> * For searches and help try: >>>>>>> * http://www.stata.com/help.cgi?search >>>>>>> * http://www.stata.com/support/statalist/faq >>>>>>> * http://www.ats.ucla.edu/stat/stata/ >>>>>>> >>>>>> >>>>> >>>>> * >>>>> * For searches and help try: >>>>> * http://www.stata.com/help.cgi?search >>>>> * http://www.stata.com/support/statalist/faq >>>>> * http://www.ats.ucla.edu/stat/stata/ >>>>> >>>>> >>>>> * >>>>> * For searches and help try: >>>>> * http://www.stata.com/help.cgi?search >>>>> * http://www.stata.com/support/statalist/faq >>>>> * http://www.ats.ucla.edu/stat/stata/ >>>>> >>>> >>>> * >>>> * For searches and help try: >>>> * http://www.stata.com/help.cgi?search >>>> * http://www.stata.com/support/statalist/faq >>>> * http://www.ats.ucla.edu/stat/stata/ >>>> >>> >>> * >>> * For searches and help try: >>> * http://www.stata.com/help.cgi?search >>> * http://www.stata.com/support/statalist/faq >>> * http://www.ats.ucla.edu/stat/stata/ >>> >> >> * >> * For searches and help try: >> * http://www.stata.com/help.cgi?search >> * http://www.stata.com/support/statalist/faq >> * http://www.ats.ucla.edu/stat/stata/ >> > > * > * For searches and help try: > * http://www.stata.com/help.cgi?search > * http://www.stata.com/support/statalist/faq > * http://www.ats.ucla.edu/stat/stata/ > * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

**References**:**st: mfx-Elasticity for a dummy variable***From:*Nyasha Tirivayi <ntirivayi@gmail.com>

**Re: st: AW: mfx-Elasticity for a dummy variable***From:*Nyasha Tirivayi <ntirivayi@gmail.com>

**Re: st: AW: mfx-Elasticity for a dummy variable***From:*A Loumiotis <antonis.loumiotis@gmail.com>

**Re: st: AW: mfx-Elasticity for a dummy variable***From:*A Loumiotis <antonis.loumiotis@gmail.com>

**Re: st: AW: mfx-Elasticity for a dummy variable***From:*A Loumiotis <antonis.loumiotis@gmail.com>

**Re: st: AW: mfx-Elasticity for a dummy variable***From:*Nyasha Tirivayi <ntirivayi@gmail.com>

**Re: st: AW: mfx-Elasticity for a dummy variable***From:*A Loumiotis <antonis.loumiotis@gmail.com>

**Re: st: AW: mfx-Elasticity for a dummy variable***From:*Nyasha Tirivayi <ntirivayi@gmail.com>

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